This invention relates to planetary type power transmissions and, more particularly, to such transmissions providing at least seven forward speed ratios and one reverse speed ratio.
Automatic shifting power transmissions are currently used in a majority of the vehicles produced in the United States. These vehicles generally employ three- and four-speed power transmissions. More recently, a trend towards more ratios, such as five- and six-speed power transmissions, has been proposed. In fact, some manufacturers do provide five-speed transmissions. Many of the vehicles utilizing manual type transmissions or countershaft type transmissions employ five- and six-speed power transmissions.
The five- and six-speed power transmissions provide improved vehicle acceleration performance and fuel economy when compared with three- and four- speed transmissions. Seven-speed transmissions offer further vehicle acceleration performance and fuel economy improvement over five- and six-speed transmissions. However, seven-speed power transmissions have not been proposed due to the complexity of these assemblies, as well as size and cost. There are many current patents that describe five- and six-speed power transmissions. Some of the six-speed power transmission patents, especially those assigned to the assignee of the present invention, describe six-speed power transmissions in families, wherein one or more family members incorporate a seven-speed power transmission. However, many of these seven-speed transmissions do not offer attractive ratio progressions.
It is an object of the present invention to provide an improved family of multi-speed planetary transmissions.
In one aspect of the present invention, each family member has three planetary gearsets each of which has a first, a second, and a third planetary member.
In another aspect of the present invention, a first member of the first planetary gearset and a first member of the second planetary gearset are continuously interconnected by a first interconnecting member.
In yet another aspect of the present invention, a second member of the first planetary gearset and a second member of the second planetary gearset are continuously interconnected by a second interconnecting member.
In still another aspect of the present invention, a third member of the second planetary gearset is continuously interconnected with a first member of the third planetary gearset.
In yet still another aspect of the present invention, a second member of the third planetary gearset is continuously interconnected with a stationary housing member such as the transmission case.
In a further aspect of the present invention, a transmission output shaft is continuously connected with at least one member of one of the planetary gearsets; and a transmission input shaft, which only interconnects selectively with members of the planetary gearsets.
In a still further aspect of the present invention, a first, second, and third torque-transmitting mechanism selectively interconnect the input shaft with at least one member of one of the planetary gearsets or with one of the interconnecting members. In a yet still further aspect of the present invention, a fourth torque-transmitting mechanism selectively interconnects a member of one of the planetary gearsets or one of the interconnecting members with either the input shaft, the output shaft, another member of one of the planetary gearsets, or with the transmission housing.
In yet a further aspect of the present invention, a fifth torque-transmitting mechanism selectively interconnects a member of one of the planetary gearsets with the output shaft, another member of one of the planetary gearsets, or with the stationary housing.
In a yet still further aspect of the present invention, a sixth torque-transmitting mechanism selectively interconnects a member of one of the planetary gearsets with a stationary housing of the transmission.
In a still further aspect of the present invention, the six torque-transmitting mechanisms are selectively engageable in combinations of two to establish at least seven forward speed ratios and one reverse speed ratio between the input shaft and the output shaft through the planetary gearsets.